Semiconductor switch with IGBT and thyristor

Abstract: In a complex semiconductor device, an IGBT and a thyristor are formed in an identical semiconductor substrate (1) to be connected in parallel with each other between main electrodes (2, 3) such that an end of the thyristor on the cathode side is connected to the main electrode via an insulated gate electrode (4) of the IGBT. Thanks to the complex of the IGBT and the thyristor, there is attained a semiconductor device having a satisfactory ignition characteristic, a low on-state voltage, and a high breakdown voltage.

Description: The present invention relates to a semiconductor device capable to being turned on and off by an insulated gate electrode, and in particular, to a complex semiconductor device having a reduced resistance loss in the on state and being particularly suitable for developing a high breakdown voltage or allowing a large current. Due to requirement of high performance of power transducers including inverter systems, it has been desired to develop a high-speed semiconductor switching device attended with a reduced loss. Recently, as a semiconductor device satisfying the requirement, an insulated gate bipolar transistor (IGBT) has attracted attentions. The IGBT has, when compared with a metal insulator semiconductor field effect transistor (MISFET), features of a decreased on-state voltage. Moreover, as compared with device of a current control type such as a GTO thyristor, the IGBT has advantages, for example, it has a higher operation speed and its gate circuit is simple and can be implemented in a compact structure. Consequently, centered on an inverter of a relatively small capacity, the application range thereof is expanding. Such an IGBT has been described, for example, in pages 220 to 225 of the Proceedings of 1991 International Symposium on Power Semiconductor Devices & ICs, Tokyo. Fig. 15 shows a schematic cross-sectional configuration of the IGBT. In the diagram, numeral 400 indicates an n - -type layer adjacent to a principal surface 411, numeral 401 denotes an n - -type layer which is adjacent to the n - -type layer 400 and which has an impurity concentration higher than that of the layer 400, numeral 402 designates a p + -type layer adjacent to the n - -type layer 401 and a principal surface 412, numeral 403 stands for a p-type layer which extends from the principal surface 411 into the n - -type layer 400 and which has an impurity concentration higher than that of the layer 400, numeral 404 indicates an n + -type layer which extends from the principal surface 411 into the p-type layer 403 and which has an impurity concentration higher than that of the layer 403, numeral 405 denotes a cathode electrode which is brought into contact with the n + -type layer 404 and the p-type 403 in the principal surface 411, a numeral 406 designates an anode electrode being brought into contact with the p + -type layer 402 in the principal surface 412, and numeral 407 stands for an insulated gate electrode formed via an insulation layer 408 at least on the p-type layer 403 on the principal surface 411. The semiconductor device includes a pnp transistor (Q 1 ) including the p + -type layer 402, the n - -type layer 400, and the p-type layer 403; an npn transistor (Q 2 ) including the n - -type layer 400, the p-type layer 403, and the n + -type layer 404; and an n-channel MISFET (M 1 ) including the insulated gate electrode 407, the n + -type layer 404, the p-type layer 403, and the n - -type layer 400. Ordinarily, since the p-type layer 403 is designed to have a sufficiently small lateral resistance r, the npn transistor (Q 2 ) has not a chance to operate. Namely, the semiconductor above can be regarded as a complex of an MISFET and a pnp transistor. Fig. 16 shows an equivalent circuit of the semiconductor device of Fig.15. Next, the operation principle will be described by reference to Figs. 15 and 16. First, to turn the semiconductor device on, a negative potential and a positive potential are applied respectively to the cathode electrode 405 and the anode electrode 406 such that the insulated gate electrode 407 is applied with a potential which is larger in terms of positive potential than that of the cathode electrode 405. Resultantly, on the surface of the p-type layer 403 below the insulated gate electrode 407, there is formed an inversion layer (channel) such that a short circuit is established between the n + -type layer 404 and the n - -type layer 400 to turn the n-channel MISFET (M 1 ) on. As a result, electrons (MIS current) injected from the cathode electrode 405 via the MISFET (M 1 ) pass through the n - -type layer 400 to flow into the p + -type layer 402, thereby injecting holes from the p + -type layer 402 into the n - -type layer 400. The carriers are consequently accumulated to cause a conductivity modulation in the n - -type layer 400 so as to lower the resistance R of the n - -type layer 400, which sets the semiconductor device to the on state. Since the lateral resistance r of the p-type layer 403 is designed to be sufficiently small, a parasitic thyristor including the n + -type layer 404, the p-type layer 403, the n - -type layer 400, and the p + -type layer 402 (including Q 1 and Q 2 ) cannot be easily operated. On the other hand, to turn the semiconductor device off, the potential of the insulated gate electrode 407 is set to be equal to or lower than that of the cathode electrode 405 to extinguish the inversion layer on the surface of the p-type layer 403 below the electrode 407 such that injection of electrons from the n + -type layer 404 is interrupted. Resultantly, injection of holes from the p + -type layer 402 is also stopped to set the semiconductor device to the off state. In the IGBT above, since there occurs the conductivity modulation in the n - -type layer 400 due to injection of holes from the p + -type layer 402, there can be characteristically developed an on-state voltage lower than that of the MISFET. Furthermore, since electrons from the n + -type layer 404 serving as an emitter of the bipolar transistor are instantaneously injected or interrupted by the gate potential, there can be conducted a switching operation at as high a speed as the MISFET. In addition, there has been recently proposed a new-type semiconductor device in which a thyristor is controlled by an insulated gate electrode. Such a device has been discussed, for example, in pages 256 to 260 of the Proceedings of 1992 International Symposium on Power Semiconductor Devices & ICs, Tokyo. Fig. 18 shows a semiconductor device described in conjunction with Fig. 1 of the article above. The device includes an n - -type layer 500 adjacent to a principal surface 511, an n-type layer 501 which is adjacent to the n - -type layer 500 and which has an impurity concentration higher than that of the n - -type layer 500, a p 1 + -type layer 502 which is adjacent to the n-type layer 501 and a principal surface 512 and which has an impurity concentration higher than that of the n-type layer 501, a p 2 + -type layer 503 which extends from the principal surface 511 into the n - -type layer 500 and which has an impurity concentration higher than that of the n - -type layer 500, a p - -type layer 504 which is adjacent to the p 2 + -type layer 503, which extends from the principal surface 511 into the n - -type layer 500, and which has an impurity concentration between those respectively of the n - -type layer 500 and the p 2 + -type layer 503, an n 1 + -type layer 505 which extends from the principal surface 511 into the p 2 + -type layer 503 and the p - -type layer 504 and which has an impurity concentration higher than that of the p 2 + -type layer 503, an n 2 + -type layer 506 which extends at a position apart from the n 1 + -type layer 505 from the principal surface 511 into the p - -type layer 504 and which has an impurity concentration higher than that of the p - -type layer 504, a cathode electrode 509 being brought into contact with the n 1 + -type layer 505 and the p 2 + -type layer 503, an anode electrode 510 being brought into contact with the p 1 + -type layer 502, a first insulated gate electrode G 1 formed via an insulation layer on an exposed surface of the p - -type layer 504 exposed between the n 1 + -type layer 505 and the n 2 + -type layer 506, and a second insulated gate electrode G 2 formed via an insulation layer on an exposed surface of the p - -type layer 504 exposed between the n - -type layer 500 and the n 2 + -type layer 506. The semiconductor device has therein a thyristor including a pnp transistor (Q 1 ) including the p 1 + -type layer 502, the n - -type layer 500, and the p - -type layer 504 and an npn transistor (Q 2 ) including the n - -type layer 500, the p - -type layer 504, and the n 2 + -type layer 506. Moreover, the device has an n-channel MISFET (M 1 ) including the first insulated gate electrode G 1 , the n 1 + -type layer 505, the p - -type layer 504, and the n 2 + -type layer 506 and an n-channel MISFET (M 2 ) including the second insulated gate electrode G 2 , the n 2 + -type layer 506, the p - -type layer 504, and the n - -type layer 500. In addition, as a parasitic element, there is included a parasitic thyristor including the n 1 + -type layer 505, the p 2 + -type layer 503, the n - -type layer 500, and p 1 + -type layer 502. Fig.19 shows an equivalent circuit of the semiconductor device of Fig. 18. The operation principle will be next described by reference to Figs. 18 and 19. First, to turn the semiconductor device on, a negative potential and a positive potential are applied respectively to the cathode electrode 509 and the anode electrode 510 such that each of the first and second insulated gate electrodes G 1 and G 2 is applied with a potential larger in terms of positive potential than that of the cathode electrode 509. Resultantly, an inversion layer is formed in the surface of the p - -type layer 504 below the first and second insulated gate electrodes G 1 and G 2 such that a short circuit is formed between the n 1 + -type layer 505, n 2 + -type layer 506, and the n - -type layer 500, thereby turning the n-channel MISFETs (M 1 and M 2 ). As a result, electrons (MIS current) injected from the cathode electrode 509 via the n-channel MISFETs (M 1 and M 2 ) pass the n - -type layer 500 to flow into the p 1 + -type layer 502, and then holes are injected from the p 1 + -type layer 502 into the n - -type layer 500. When the hole current reaches the p - -type layer 504 and flows into the cathode electrode 509, there appears a potential difference due to a lateral resistance r 2 of the p - -type layer 504. When the potential difference exceeds a diffusion potential between the p - -type layer 504 and the n 2 + -type layer 506 (about 0.7 V for silicon at the room temperature), electrons are directly injected from the n 2 + -type layer 506 into the n - -type layer 500 and hence the thyristor is ignited and the semiconductor device is set to the on state. In this connection, the resistor r 1 is sufficiently small due to the high impurity concentration of the p 2 + -type layer 503. Consequently, the parasitic thyristor including Q 3 and Q 4 cannot be easily turned on. On the other hand, to turn the device off, the potential of the first and second insulated gate electrodes G 1 and G 2 is set to be equal to or less than that of the cathode electrode 509 such that the inversion layer in the surface of the p - -type layer 504 below the first and second insulated gate electrodes G 1 and G 2 is extinguished to interrupt injection of electrons from the n 2 + -type layer 506. This resultantly interrupts injection of holes from the p 1 + -type layer and hence the semiconductor is set to the off state. The semiconductor device of this type has the following feature. Namely, thanks to the thyristor operation, electrons supplied from the cathode electrode 509 via the n-channel MISFET (M 1 ) flows in a state where the electrons are extended in the lateral direction of the n 2 + -type layer 506 and hence the on-state voltage (resistance loss) in the conductive state can be minimized as compared with the conventional IGBT. In addition, the device can be turned on and off respectively according to application and removal of the potential onto and from the insulated gate electrode. This leads to a feature that the gate circuit is quite simplified like in the case of the conventional IGBT. However, among the semiconductor devices, the IGBT is attended with a problem, due to difficulty of obtaining a high breakdown voltage and a large current, that the IGBT cannot be easily applied to an inverter having a large capacity. Fig. 17 shows simulation results of lines of current flow on the cathode side in the stationary on state of the IGBT. Electrons flowing from the cathode electrode 405 via the inversion layer (n channel) to the n - -type layer 400 are slightly extended in the lateral direction by an n + -type accumulation layer formed in the surface of the n - -type layer 400 just below the gate electrode 407. However, according to influence from the large resistance of the n + -type accumulation layer, the electrons cannot be fully extended. In consequence, in a position apart from the cathode electrode 405 (below the right insulated gate electrode , the current is not easily flown and hence the on-state voltage becomes larger. On the other hand, in a region below the p-type layer 403, due to depletion caused by a potential drop in the n - -type layer 400, the current is not easily flown. This phenomenon is more remarkable when the impurity concentration of the n - -type layer 400 becomes lower to attain a higher breakdown voltage. Namely, for a higher breakdown voltage, the gate length is required to be elongated, which in turn results in deterioration of extension of the current flow in the lateral direction. In other words, the electron supply from the cathode side is decreased and the conductivity modulation effect is reduced. Consequently, when the breakdown voltage of the IGBT is increased, the on-state voltage becomes considerably higher, which leads to a problem of difficulty in increasing the capacity. Moreover, the thyristor of the MIS gate type above is attended with a problem that the thyristor cannot be easily ignited. In the conventional device, as described above, when the device is turned on, an inversion layer is first formed in the surface of the p - -type layer 504 below the insulated gate electrodes G 1 and G 2 and then the n-channel MISFETs (M 1 and M 2 ) are turned on to form a short circuit between the n 1 + -type layer 505, the n 2 + -type layer 506, and the n - -type layer 500. Resultantly, as can be seen from the equivalent circuit of Fig. 19, electrons (MIS current) injected from the cathode electrode 509 into the n - -type layer 500 are required to pass the inversion layers (channels) of the two MISFETs M 1 and M 2 and hence the electron current is limited due to the channel resistance. In consequence, since the hole current from the p 1 + -type layer 502 is small, the thyristor is not easily ignited. To prevent this phenomenon, there may be employed a method of increasing the area (channel width) of M 2 or decreasing the area of the n 2 + -type layer 506. This however means that the area of the thyristor through which the main current is passed in minimized in the overall semiconductor device. Consequently, the resistance loss (on-state voltage) in the conductive state is increased, which leads to a problem similar to that of the conventional IGBT. Moreover, in the MIS gate-type thyristor, the p - -type layer 504 is connected via the p - -type layer 503 to the cathode electrode; consequently, it is difficult to ignite the thyristor. Namely, the voltage drop caused by the lateral resistance r 2 of the p - -type layer occurs particularly in the vicinity of the cathode electrode and is hence small. In consequence, the thyristor is not ignited in the region. As a result, there arises a problem that only a portion of the thyristor is ignited and hence the on-state voltage is increased. US-A-4847671 discloses a complex semiconductor device in which, in one embodiment, there is a first semiconductor layer and a second semiconductor layer between the first layer and one principal surface of the device, a third semiconductor layer of the second conductivity type extending from a second principal surface into the first layer, a fourth semiconductor layer of the first conduction type extending into the third layer from the second principal surface, a fifth semiconductor layer extending from the second principal surface, and a sixth semiconductor layer between the first and fifth layers, to separate them. The first, fourth and fifth layers are of one conduction type and the second, third and sixth layers are of a second conduction type. The second layer has an impurity concentration higher that the first. There is also a first electrode in contact with the second layer, a second electrode in contact with the third and fourth layers and a control electrode separated by an insulation layer from the second principal surface. JP-A-5-029607 discloses a MIS gate control thyristor in which there are first to fifth semiconductor layers, similar to US-A-4847671 but the third layer surrounds both the third and fifth layers and has a heavily doped part in contact with the third, but not the fifth layer. The present invention seeks to provide a complex semiconductor device having an insulated gate electrode developing a small resistance loss (on-state voltage) in the conductive state and being suitable for a high breakdown voltage, thereby removing the drawbacks of the prior art. According to the present invention there is provided a complex semiconductor device comprising: a semiconductor substrate including a pair of principal surfaces, a first semiconductor layer of a first conduction type, a second semiconductor layer of a second conduction type being adjacent to the first principal surface and the first semiconductor layer and having an impurity concentration higher than that of the first semiconductor layer, a third semiconductor layer of the second conduction type extending from a second principal surface into the first semiconductor layer and having an impurity concentration higher than that of the first semiconductor layer, a fourth semiconductor layer of the first conduction type extending from the second principal surface into the third semiconductor layer and having an impurity concentration higher than that of the third semiconductor layer, a fifth semiconductor layer of the first conduction type extending from the second principal surface into the first semiconductor layer, being partially brought into contact with the third semiconductor layer and when with the first semiconductor layer, being apart from the fourth semiconductor layer, and having an impurity concentration higher than that of the third semiconductor layer, and a sixth semiconductor layer of the second conduction type being disposed between the first and fifth semiconductor layers, at least one gap being defined between the sixth and the third semiconductor layers to permit said contact of said first and fifth layers and having an impurity concentration between those respectively of the first and fifth semiconductor layers; a first main electrode (3) being brought into contact via a low resistance with the second semiconductor layer in the first principal surface of the semiconductor substrate; a second main electrode (2) being brought into contact via a low resistance with the third and fourth semiconductor layers in the second principal surface of the semiconductor substrate; and a control electrode (4) formed via an insulation layer on a surface of the third semiconductor layer exposed between the fourth and fifth semiconductor layers in the second principal surface of the semiconductor substrate. Embodiments of the present invention will now be described, by way of example, with reference to accompanying drawings wherein: Fig. 1 is a schematic cross-sectional view showing an embodiment of a complex semiconductor device according to the present invention; Fig. 2 is an equivalent circuit diagram of the complex semiconductor device shown in Fig. 1; Fig. 3 is a diagram showing lines of current flow in the on state of the complex semiconductor device shown in Fig. 1; Figs. 4A and 4B are a schematic plan view and a perspective cross-sectional view showing a specific example of the complex semiconductor device shown in Fig. 1; Figs. 5A and 5B are a schematic perspective cross-sectional view and a schematic plan view showing the configuration of another embodiment of the complex semiconductor device according to the present invention; Fig. 6 is a schematic cross-sectional view of A-A and B-B line portions in the embodiment shown in Fig. 5B; Fig. 7 is a schematic cross-sectional view of a C-C line portion in the embodiment shown in Fig. 5B Fig. 8 is an equivalent circuit diagram of the complex semiconductor device shown in Figs. 5A and 5B; Figs. 9A and 9B are diagrams showing lines of current flows respectively in a complex semiconductor device according to the present invention and a known complex semiconductor device; Fig. 10 is a schematic plan view showing a second configuration example formed by altering the configuration and the arranging position of the notched portions of the p-type layer in the embodiment of Figs. 12A and 12B; Fig. 11 is a schematic plan view showing a third configuration example formed by altering the configuration and the arranging positions of the notched portions of the p-type layer in the embodiment of Figs. 12A and 12B; Fig.12 is a schematic plan view showing a third configuration example formed by altering the configuration and the arranging position of the notched portions of the p-type layer in the embodiment of Figs. 12A and 12B; Figs. 13A to 13C are schematic cross-sectional views of A-A, B-B, C-C, D-D, and E-E line portions in the respective configuration examples shown in Figs. 10 to 12; Fig.14 is a schematic circuit diagram showing an example of the configuration of an inverter to drive a motor employing a complex semiconductor device according to the present invention; Fig. 15 is a schematic cross-sectional view of an IGBT presented as a prior technology of the present invention; Fig. 16 is an equivalent circuit diagram of the IGBT shown in Fig. 15 ; Fig. 17 is a diagram showing lines of current flow in the on state of the IGBT shown in Fig.15 ; Fig.18 is a schematic cross-sectional diagram of a semiconductor device as a prior technology of the present invention in which a thyristor is controlled by an insulated gate electrode; and Fig. 19 is an equivalent circuit diagram of the semiconductor device shown in Fig. 18. Referring now to the drawings, description will be given of embodiments according to the present invention. Fig. 1 is a schematic cross-sectional view showing an embodiment of a complex semiconductor device according to the present invention. In the diagram, numeral 1 indicates a semiconductor substrate including a pair of principal surfaces 11 and 12, an n-type layer 13 including a first layer portion 131 (n - ) formed apart from the principal surfaces and a second layer portion 132 which is adjacent to the first layer portion 131 and which has an impurity concentration higher than that of the layer 131, a p 1 + -type layer which is adjacent to the second layer portion 132 of the n-type layer 13 and the principal surface 12 and which has an impurity concentration higher than that of the layer 132, a p-type layer 15 including a first layer portion 151 which is adjacent to the principal surface 11 and the first layer portion 131 of the n-type layer 13 and which has an impurity concentration higher than that of the layer 131 and a second layer portion 152 which extends from the principal surface 11 into the first layer portion 151 and which has an impurity concentration higher than that of the layer 151, an n 1 + -type layer 16 which extends from the principal surface 11 into the p-type layer 15, a substantial portion of which is adjacent to the second layer portion 152, and which has an impurity concentration higher than that of the layer 152, an n 2 + -type layer 17 which is adjacent to the principal surface 11, which extends into the portion 131 of the n-type layer 13 and the portion 151 of the p-type layer 15, and which has an impurity concentration higher than those of both layers 131 and 151, and a p - -type layer 18 which is formed apart from the portion 151 of the p-type layer 15 between the portion 131 of the n-type layer 13 and the n 2 + -type layer 17, and which has an impurity concentration between those of the layers 131 and 17. Numeral 2 indicates a cathode electrode which is brought into contact via a low resistance with the n 1 + -type layer 16 and the portion 152 of the p-type layer 15 in the principal surface 11 of the semiconductor substrate, a numeral 3 denotes an anode electrode which is brought into contact via a low resistance with the p 1 + -type layer 14, and a numeral 4 designates an insulated gate electrode which is mounted via an insulated layer 5 on a surface of the portion 151 of the p-type layer 15 exposed in the principal surface 11 of the semiconductor substrate between the n 1 + -type layer 16 and the n 2 + -type layer 17. The portion 152 of the p-type layer 15 is, at a position apart from the electrode 4, adjacent to the n 1 + -type layer 16, whereas the p - -type layer 18 is, at a position apart from the electrode 4, adjacent to the n 2 + -type layer 17. The complex semiconductor device has therein a thyristor including a pnp transistor (Q 1 ) including the p 1 + -type layer 14, the n-type layer 13, and the p - -type layer 18 and an npn transistor (Q 2 ) including the n-type layer 13, the p - -type layer 18, and the n 2 + -type layer 17. In addition, there exists an IGBT region including an n-channel MISFET (M 1 ) including the insulated gate electrode 4, the n 1 + -type layer 16, the portion 151 of the p-type layer 15, and the n 2 + -type layer 17; an npn transistor (Q 3 ) including the n 1 + -type layer 17, the p-type layer 15, and the n-type layer 13; and a pnp transistor (Q 4 ) including the p-type layer 15, the n-type layer 13, and the p 1 + -type layer 14. Namely, the complex semiconductor device of Fig. 1 can be regarded as a complex device in which, as indicated by the equivalent circuit of Fig. 2, the IGBT and the thyristor are connected on the cathode side by the common n-channel MISFET (M 1 ). Next, the operation principle will be described by reference to Figs. 1 and 2. First, to turn the complex semiconductor device on, a negative potential and a positive potential are applied respectively to the cathode and anode electrodes 2 and 3 such that the insulated gate electrode 4 is applied with a potential larger in terms of positive potential than that of the cathode electrode 2. Resultantly, an inversion layer (channel) is formed in a surface of the portion 151 of the p-type layer 15 below the insulated gate electrode 4 and hence the n 1 + -type layer 16 is connected via the inversion layer of the portion 131 of the n-type layer 13 to the n 2 + -type layer 17, thereby turning the so-called n-channel MISFET (M 1 ) on. As a result, electrons (MIS current) injected from the cathode electrode 2 via the n-channel MISFET (M 1 ) pass the n-type layer 13 and then flow into the p 1 + -type layer 14. This causes the pnp transistors (Q 1 and Q 3 ) to operate and hence holes are injected from the p 1 + -type layer 14 into the n-type layer 13. When the hole current flows into the p - -type layer 18, the potential of the p - -type layer 18 is increased. When the potential difference exceeds the diffusion potential between the p - -type layer 18 and the n 2 + -type layer 17 (about 0.7 V in silicon at the room temperature), the npn transistor (Q 2 ) operates and then electrons are injected from the n 2 + -type layer 17 directly into the n-type layer 13. As a result, the thyristor including the pnp transistor (Q 1 ) and the npn transistor (Q 2 ) ignites so as to thereby set the complex semiconductor device to the on state. In this regard, the resistance r 2 is sufficiently small due to the high impurity concentration of the portion 152 of the p-type layer 15 and hence a parasitic thyristor including the n 1 + -type layer 16, the portion 152 of the p-type layer 15, the n-type layer 13, and the p 1 + -type layer 14 cannot be easily turned on. Moreover, the portion 132 of the n-type layer 13 having a relatively high impurity concentration suppresses the hole injection effect of the pnp transistors (Q 1 and Q 3 ) and is disposed to prevent the latch-up of the parasitic thyristor and to decrease the loss due to a tail current in a turn-off operation. Consequently, the impurity concentration and the thickness thereof are to be set according to characteristics of the desired complex semiconductor device and hence there may be employed another means only if the hole injection effect can be suppressed by the means. For example, there may be disposed a construction in which the portion 132 of the n-type layer 13 is partially connected to the anode electrode 3 via a short circuit or there may be included means to lower the lifetime of minority carriers in the portion 132 in the vicinity of junction between the p 1 +type layer 14 and the n-type layer 13. On the other hand, to turn the device off, the potential of the insulated gate electrode 4 is set to a value equal to or less than that of the cathode electrode 2 such that the inversion layer is resultantly extinguished from the surface of the portion 151 of the p-type layer 15 below the insulated gate electrode 4. The electron injection from the n 1 + -type layer 16 into the n 2 + -type layer 17 is interrupted and that from the n 2 + -type layer 17 into the n-type layer 13 is simultaneously interrupted. As a result, the hole injection from the p 1 + -layer 14 is stopped and hence the complex semiconductor device is set to the off state. Fig. 3 shows simulation results of lines of current flow on the side of the cathode electrode 2 in the stationary on state of the complex semiconductor device of Fig. 1. Since the thyristor region is added to the IGBT in the best form, when compared with lines of current flows of the conventional IGBT shown in Fig. 28, electrons supplied from the cathode electrode 2 via the MIS channel uniformly flow in a state where the electrons are fully extended in the thyristor region. Consequently, the on-state voltage can be sufficiently lowered. Furthermore, since the portion 151 of the p-type layer 15 disposed in the IGBT region is separated from the p - -type layer 18 disposed in the thyristor region, the n 2 + -type layer 17 of the thyristor region is partially brought into contact with the n-type layer 13, thereby controlling the MIS current and the thyristor current by one n-channel MISFET (M 1 ). Namely, the MIS current necessary to ignite the thyristor is required to pass only one channel resistance. Moreover, in the thyristor section, the current passes only one channel resistance. Consequently, the thyristor can be easily ignited by a small MISFET region (channel width). Capability of minimizing the small MISFET region (channel width) means that the area of the thyristor in the overall device can be increased and hence the on-state voltage can be sufficiently decreased. Moreover, since the p - -type layer 18 of the thyristor region is floating in potential with respect to the p-type layer 15, the potential of the p - -type layer 18 can be easily and uniformly increased due to the hole current supplied. As a result, the thyristor can be easily ignited, and the overall thyristor region contributes to the operation; consequently, the on-state voltage can be sufficiently reduced. That is, a high breakdown voltage and a large current can be easily achieved. In addition, since the area of the insulated gate electrode can be remarkably minimized as compared with the conventional device, there is required only a small charge/discharge current of the gate. This leads to an advantage that the switching operation speed is increased and the gate circuit size is decreased. Furthermore, the complex semiconductor device of Fig. 1 can be easily turned on and off by applying and removing a potential to and from the insulated gate electrode. Thanks to adoption of the saturation characteristic of the n-channel MISFET (M 1 ), there is attained an aspect of a current limiting action even in the thyristor operation. Ordinarily, when manufacturing the semiconductor devices, the structure of Fig. 1 is adopted as a cell such that each product includes several hundred to several tens of thousand of cells integrated in an identical semiconductor substrate for a parallel operation thereof. In this situation, when the current limiting action is possessed by each cell, the current cannot be concentrated onto any particular one cell but is uniformly loaded onto the respective cells and hence it is possible to prevent destruction of the semiconductor device due to the current concentration. Namely, there is obtained an advantage that by quite a simplified gate circuit, the on and off control of the semiconductor device can be conducted with a current larger than that of the conventional device without destroying the device. Figs. 4A and 4B are a plan view and a cross-sectional bird's-eye view showing a specific example of a unitary cell of a semiconductor device similar to the embodiment of Fig. 1. Description will be given only the portions different from the associated portions of Fig. 1. The cathode electrode 2, which is disposed on the overall surface of the principal surface 11, establishes an ohmic contact with the n 1 + -type layer 16 and the portion 152 of the p-type layer 15 and is electrically insulated by an insulation layer 6 from the insulated gate electrode 4 and the n 2 + -type layer 17. However, in the diagram, for easy understanding of the shape of the insulated gate electrode, the cathode electrode 2 and the insulation layer 6 are partially removed. With the provision above, the fine machining of the cathode electrode 2 is unnecessitated; moreover, the electric resistance in each region from the cathode electrode 2 to the n 1 + -type layer 16 and the portion 152 of the p-type layer 15 of each cell can be minimized. In addition, there is attained an effect of improving the heat dissipation efficient from the semiconductor substrate 1. In this regard, the right and left insulated gate electrodes 4 shown in this diagram are not independent of each other but are connected to each other at a position not shown in the diagram. Figs. 5A and 5B show the configuration of another embodiment of the complex semiconductor device of the present invention. Fig. 5A is a schematic perspective cross-sectional view in which the cathode electrode and the insulation layer are partially removed, whereas Fig. 5B is a plan view in which the cathode electrode and the insulation layer are partially removed in the similar manner. In Figs. 5A and 5B, numeral 1 indicates a semiconductor substrate, numeral la denotes a principal surface, numeral 1b designates another principal surface, numeral 2 stands for an n-type layer of a low impurity concentration (n - -type layer, first semiconductor layer), numeral 3 indicates an n-type impurity layer (n-type layer, first semiconductor layer,) which is adjacent to the n - -type layer 2 on the side of the principal surface la and which has an impurity concentration higher than that of the n - -type layer 2, numeral 4 denotes a first p-type layer having a high impurity concentration (p 1 + -type layer, second semiconductor layer) which is adjacent to the n-type layer 3 on the side of the principal surface la, a numeral 5 designates two band-shaped p-type impurity layers (p-type layer, third semiconductor layer) which are disposed in the n - -type layer 2 in the principal surface 1b to be parallel to a pair of opposing edges of the semiconductor substrate 1 and to be apart from each other, numeral 6 similarly stands for two band-shaped second p-type layers having a high impurity concentration (p 2 + -type layer, third semiconductor layer) which are disposed in portions of two band-shaped p - -type layers 5 along the longitudinal direction of the p-type layers 5, numeral 7 similarly indicates two band-shaped first n-type layers having a high impurity concentration (n 1 + -type layer, fourth semiconductor layer) which are disposed in portions of two band-shaped p 2 + -type layers 6 along the longitudinal direction of the p 2 + -type layers 6, numeral 8 denotes a second n-type layer having a high impurity concentration (n 2 + -type layer, fifth semiconductor layer) which is disposed in the n - -type layer 2 in the principal surface 1b and which has both side edge portions to be respectively brought into contact with opposing side edge portions of two band-shaped p-type layers 5, numeral 9 designates a p-type layer having a low impurity concentration (p - -type layer, sixth semiconductor layer) which is disposed between the n - -type layer 2 and the n 2 + -type layer 8 and which has a plurality of notched portions 9a for partially providing a direct contact between the n - -type layer 2 and the n 2 + -type layer 8, numeral 10 stands for two long insulated gate electrodes (G) which are mounted via an insulation layer 11 on the surface of the p-type layer 5 exposed between the n 1 + -type layer 7 and the n 2 + -type layer 8, numeral 12 indicates an insulation layer disposed to cover a portion of the exposed surface of the n 1 + -type layer 7, two insulated gate electrode (G), and the exposed surface of the n 2 + -type layer 8, numeral 13 denotes an anode electrode (A) disposed in a low-resistance contacting state on the p 1 + -type layer 4 on the principal surface la, and numeral 14 designates a cathode electrode (K) disposed to establish a low-resistance contact with the respective exposed surfaces of the p 2 + -type layer 6 and the n 1 + -type layer 7 and to cover the insulation layer 12. Moreover, the n - -type layer 2 and the n-type layer 3 form the first semiconductor layer, whereas the p-type layer 5 and the p 2 + -type layer 6 constitute the third semiconductor layer. The n - -type layer 2, the n-type layer 3, the p 1 + -type layer 4, the p-type layer 5, the p 2 + -type layer 6, the n 1 + -type layer 7, the n 2 + -type layer 8, and p - -type layer 9 configure as a whole the semiconductor substrate 1. In addition, the plural notched portions 9a disposed in the p - -type layer 9 are of a band shape and extend in a direction substantially vertical to a pair of opposing edges of the substrate 1, namely, a direction substantially vertical to the longitudinal direction of the insulated gate electrodes (G) 12. Furthermore, the notches 9a are arranged with an equal interval therebetween along the longitudinal direction of the electrodes (G) 12. In this case, as for the portion where the p - -type layer 9 is arranged, the p - -type layer 9 intervenes between the n - -type layer 2 and n 2 + -type layer 8. However, as for the portions where the notched portions 9a of the p - -type layer 9 are arranged, the n - -type layer 2 and n 2 + -type layer 8 are directly coupled with each other via the notched portions 9a. Moreover, two electrodes (G) 12 are electrically connected to each other at a position not shown in the diagram. Next, Fig. 6 is a lateral cross-sectional view of the A-A and B-B line portions shown in Fig.5A, whereas Fig. 7 is a lateral cross-sectional view of the C-C portion shown in Fig. 5B. In Figs. 6 and 7, the same constituent elements as those of Figs. 5A and 5B are assigned with the same reference numerals. Furthermore, as shown in Figs. 6 and 7, the p - -type layer 9 intervenes between the n - -type layer 2 and the n 2 + -type layer 8 excepting the portions where the notched portions 9a are arranged, thereby preventing the direct contact between the n - -type layer 2 and the n 2 + -type layer 8. However, in the configuration of the portions where the notched portions 9a are fabricated, the n - -type layer 2 is directly brought into contact with the n 2 + -type layer 8. Subsequently, Fig. 8 is a circuit diagram showing an electrically equivalent circuit of the complex semiconductor device shown in Figs. 5A and 5B. In Fig. 8 , TR1 indicates a first pnp transistor including the p 1 + -type layer 4, the n - -type layer 2, and the p - -type layer 9, TR2 denotes a first npn transistor including the n - -type layer 2, the p - -type layer 9, and the n 2 + -type layer 8, TR3 indicates a second pnp transistor including the p 1 + -type layer 4, the n - -type layer 2, and the p 2 + -type layer 6, TR4 denotes a second npn transistor including the n - -type layer 2, the p 2 + -type layer 6, and the n 1 + -type layer 7, MTR1 denotes an n-channel MISFET including the insulated gate electrode (G) 10, the n 1 + -type layer 7, the p-type layer 5, and the n 2 + -type layer 8, r 0 designates a lateral resistance of the p - -type layer 9, r 1 stands for a lateral resistance of the p 2 + -type layer 6, and R indicates an internal resistance of the n - -type layer 2. Of the other constituent elements, the same elements as those shown in Figs. 5A and 5B are assigned with the same reference numerals. Furthermore, the first pnp transistor (TR1) and the first npn transistor (TR2) configure a thyristor, whereas the n-channel MISFET (MTR1), the second pnp transistor (TR3), and the second npn transistor (TR4) form an IGBT. In this way, the complex semiconductor device can be regarded as a complex semiconductor device in which, as shown in the equivalent circuit of Fig.8, the IGBT and the thyristor are commonly connected to each other by the MISFET (MTR1) on the respective cathode sides. Description will now be given of operation of the complex semiconductor device configured as above. First, to turn the device on, a negative potential and a positive potential are applied respectively to the cathode electrode (K) 14 and the anode electrode (A) 13 such that the insulated gate electrode (G) 10 is applied with a positive potential higher than that of the cathode electrode (K) 14. In this situation, an inversion layer (channel) is formed in the surface portion of the p-type layer 5 below the insulated gate electrode (G) 10 and hence the n 1 + -type layer 7 and the n 2 + -type layer 8 are connected to each other via the inversion layer to turn the n-channel MISFET (MTR1) on. Consequently, electrons (MIS current) injected from the cathode electrode (K) 14 via the n-channel MISFET (MTR1) flow from the n 2 + -type layer 8 via the n - -type layer 2 into the p 1 + -type layer 4 to set the first npn transistor (T1) to the on state so as to inject holes (hole current) from the p 1 + -type layer 4 into the n - -type layer 2. Next, when the hole current flows via the p - -type layer 9 and the n-channel MISFET (MTR1) into the p-type layer 5, the large lateral resistance r 0 of the p-type layer 5 increases the potential of the p - -type layer 9, thereby developing a potential difference between the p - -type layer 9 and the n 2 + -type layer 8. When the potential difference of the p - -type layer 9 and the n 2 + -type layer 8 exceeds the diffusion potential (about 0.7 in silicon at the room temperature), the first npn transistor (TR2) is set to the on state and hence electrons are injected from the n 2 + -type layer 8 directly into the n - -type layer 2. In consequence, the thyristor including the first pnp transistor (TR1) and the first npn transistor (TR2) ignites and the complex semiconductor device is set to the on state. In this case, the lateral resistance r 1 of the p 2 + -type layer 6 is sufficiently low due to the high impurity concentration of the p 2 + -type layer 6 and hence the parasitic thyristor including the n 1 + -type layer 7, the p 2 + -type layer 6, the n - -type layer 2, and the p 1 + -type layer 4 cannot be easily turned on. Moreover, the n-type layer 3 having a relatively high impurity concentration suppresses the hole injection efficiency in the first and second npn transistors (TR1) and (TR2). The layer 3 is inserted to prevent the latch-up of the parasitic thyristor and to reduce the loss caused by the tail current in the turn-off operation. Consequently, the impurity concentration and the thickness of the n-type layer 3 are to be appropriately set according to desired characteristics of the complex semiconductor device. In this regard, the means of suppressing the hole injection efficiency is not limited to the means setting the n-type layer 3, namely, there may be employed another means having the similar function. For example, the n-type layer 3 may be configured to be partially connected via a short circuit to the anode electrode (A) 13 or there may be disposed any known means in the junction portion between the p 1 + -type layer 4 and the n - -type layer 2 to lower the lifetime of minority carriers. On the other hand, to turn the device off, the potential applied to the insulated gate electrode (G) 10 is set to a value equal to or less than the potential applied to the cathode electrode (K) 14. In this situation, the inversion layer (channel) formed in the surface portion of the p-type layer 5 below the insulated gate electrode (G) 10 is extinguished and hence the injection of electrons flowing from the n 1 + -type layer 7 into n + -type layer 8 is interrupted. In association therewith, the injection of electrons flowing from the n 2 + -type layer 8 into the n - -type layer 2 is interrupted; consequently, the injection of holes from the p 1 + -type layer 4 into the n - -type layer 2 is stopped and hence the complex semiconductor device is set to the off state. Next, Fig.9A is a diagram for explaining simulation results of lines of current flows in the cross section of the B-B line portion of the complex semiconductor device shown in Fig.6 on the cathode side of the device in the on state. In Fig. 9A , the same constituent elements as those of Figs. 5A and 5B are assigned with the same reference numerals. As shown in Fig. 9A , according to this device, as compared with the lines of current flows on the cathode side of the known IGBT in the on state (Fig. 9B), electrons supplied from the cathode electrode (K) 14 via the channel of the MISFET (MTR1) are fully extended to uniformly flow in the thyristor region. Consequently, the inter-terminal voltage in the on-state operation (resistance in the on-state operation) can be sufficiently reduced as compared with the known IGBT. In addition, in the device, the p - -type layer 9 having a plurality of notched portions 9a are inserted between the n 2 + -type layer 8 and the n - -type layer 2 to establish a partial contact between the n 2 + -type layer 8 and the n - -type layer 2 in the thyristor region. Consequently, both of the MIS current and the thyristor current can be controlled by one MISFET (MTR1). Namely, the MIS current necessary to ignite the thyristor is required to pass only one channel resistance of the MISFET (MTR1). On the other hand, also the thyristor current passes only one channel resistance of the MISFET (MTR1). In consequence, with provision of only one small MISFET region (channel width), the thyristor can be easily ignited. Moreover, when the MISFET region (channel width) is minimized, it is possible to increase the area of the thyristor region in the overall device. This sufficiently reduces the inter-terminal voltage in the on-state operation (resistance in the on-state operation) and hence a high breakdown voltage and a large current can be easily attained for the device. Furthermore, as compared with the known semiconductor device, the area where the insulated gate electrode (G) 10 is disposed can be remarkably reduced. Consequently, only a small charge/discharge current is required for the gate, which also leads to an advantage that the switching operation speed is increased and the gate circuit size is minimized. Additionally, the complex semiconductor device can be easily turned on and off by applying and removing a potential of a predetermined polarity to and from the insulated gate electrode (G) 10. Furthermore, thanks to adoption of the saturation characteristic of the n-channel MISFET (MTR1), there is obtained an aspect of a current limiting action even in the thyristor operation. In general, when producing the device, the structure shown in Figs. 5A and 5B is used as a cell such that several hundred to several tens of thousand of cells are integrated in an identical semiconductor substrate to be connected to each other for operation in a parallel fashion. However, in the parallel operation, when each cell has the current limiting action, the current is not concentrated onto a particular cell or onto particular several cells so as to be uniformly loaded onto the respective cells. Consequently, it is advantageously possible to prevent destruction of the complex semiconductor device due to the current concentration. Next, Figs. 10 to 12 are schematic plan views showing second, third, and fourth examples in which the constitution and the arrangement positions of the notched portions of the p - -type layer 9 are respectively altered in the complex semiconductor device shown in Figs.5A and 5B. Figs. 13A to 13C are lateral cross-sectional views of A-A, B-B, C-C, D-D, and E-E line portions of Figs. 10 to 12. In Figs. 10 to 12 and Figs. 13A to 13C, numeral 9b indicates the notched portion of a second shape, numeral 9c denotes the notched portion of a third shape, numeral 9d indicates the notched portion of a fourth shape. Moreover, the same constituent elements as those shown in Figs. 5A and 5B are assigned with the same reference numerals. Furthermore, the notched portions 9b of the second shape are of a short band contour and extend in a direction substantially vertical to a pair of opposing edges of the semiconductor substrate 1, namely, to a direction substantially vertical to the longitudinal direction of the insulated gate electrode (G) 12. Moreover, the notched portions 9b extend up to an intermediate position of the p - -type layer 9 in the direction of width thereof and are arranged with an equal interval therebetween in the longitudinal direction of the insulated gate electrode (G) 12. The notched portions 9c of the third shape are of a long band shape and extend in a direction parallel to a pair of opposing edges of the semiconductor substrate 1, namely, a direction parallel to the longitudinal direction of the insulated gate electrode (G) 12. Moreover, the notched portions 9c are arranged along an intermediate position of the p - -type layer 9 in the direction of width thereof. Furthermore, the notched portions 9d of the fourth shape are of a circular contour and extend in a direction parallel to a pair of opposing edges of the semiconductor substrate 1, namely, along the longitudinal direction of the insulated gate electrode (G) 12. Moreover, the notched portions 9c are arranged with an equal interval therebetween at an intermediate position of the p - -type layer 9 in the direction of width thereof. In this case, as shown in Figs. 10 to 12 and Figs. 20A to 20C, the contacting portions of the notched portions 9b of the second shape with the n 2 + -type layer 8 and the n - -type layer 2 are limited to the portions adjacent to the insulated gate electrode (G). Consequently, in the case employing the p - -type layer 9 having such notched portions 9b, as compared with the case using the p - -type layer 9 having the notched portions 9a shown in Figs. 5A and 5B, it is possible to increase the area where the p - -type layer 9 is arranged. Namely, the non-contact portions with the n 2 + -type layer 8 and the n - -type layer 2 can be increased, thereby decreasing the inter-terminal voltage in the on-state operation (resistance in the on-state operation) of the complex semiconductor device. In addition, as shown in Figs. 11 and 12 and Figs. 13A to 13C, the contact portions of the notched portions 9c of the third shape with the n 2 + -type layer 8 and the n - -type layer 2 are disposed in a portion apart from the insulated gate electrode (G) 10 and in a band-shaped portion parallel to the electrode (G) 10. In consequence, using the p - -type layer 9 having such notched portions 9c, it is possible to increase the thyristor area adjacent to the n-channel MISFET (MTR1), thereby decreasing the inter-terminal voltage in the on-state operation (resistance in the on-state operation) of the complex semiconductor device. Furthermore, as shown in Fig. 12 and Figs. 13A to 13C, the contact portions of the notched portions 9d of the fourth shape with the n 2 + -type layer 8 and the n - -type layer 2 are separately disposed to be apart from each other in a portion apart from the insulated gate electrode (G) 10. Consequently, in a case adopting the p - -type layer 9 having such notched portions 9d, like in the case employing the notched portions 9b of the third shape, it is possible to increase the area where the p - -type layer 9 is arranged, namely, the non-contact portions with the n 2 + -type layer 8 and the n - -type layer 2. Moreover, like in the case employing the notched portions 9c of the fourth shape, it is possible to increase the thyristor area adjacent to the n-channel MISFET (MTR1). In consequence, the inter-terminal voltage in the on-state operation (resistance in the on-state operation) of the complex semiconductor device can be decreased. Incidentally, the shape of the notched portions disposed in the p - -type layer 9 is not limited to the notched portions 9a shown in Figs.5A and 5B and the notched portions 9b, 9c and 9d of the second, third, and fourth shapes. Namely, there may be disposed notched portion having another shape. In this case, when the area of non-contact portions with the n 2 + -type layer 8 and the n - -type layer 2 is decreased, the inter-terminal voltage in the on-state operation (resistance in the on-state operation) of the complex semiconductor device can be minimized, which is favorable because fears of decrease in the breakdown voltage is removed. In consequence, for the complex semiconductor device, it is desirable to adopt a structure in the plan view in which the total area of the notched portions of the p - -type layer 9 is possibly reduced under the condition that the thyristor ignition and distinction characteristics are not deteriorated. Next, Fig. 14 is an electric circuit diagram showing an example of a motor driving inverter system including the complex semiconductor device according to the present invention. In Fig. 14 , T 1 and T 2 indicate a pair of direct-current (dc) terminals connected to a dc power source, T 3 to T 5 denote alternating-current (ac) terminals disposed as many as there are phases of an alternating current (ac) connected to a three-phase induction motor; SW 11 , SW 12 , SW 21 , SW 22 , SW 31 , and SW 32 designate complex semiconductor devices of the present invention; D 11 , D 12 , D 21 , D 22 , D 31 , and D 32 stand for flywheel diodes; SB 11 , SB 12 , SB 21 , SB 22 , SB 31 , and SB 32 represent snubber circuits including a series connection of a parallel circuit of a diode and a resistor and a capacitor. Moreover, the complex semiconductor devices of the present invention SW 11 , SW 12 , SW 21 , SW 22 , SW 31 , and SW 32 form series connection circuits for three phases in which each of the circuits includes a series connection of two complex semiconductor devices selected therefrom. These series circuits are connected between the pair of dc terminals T 1 and T 2 . In this case, the series connection points of the two complex semiconductor devices SW 11 and SW 12 , SW 21 and SW 22 , and SW 31 and SW 32 are respectively connected to the ac terminals T 3 , T 4 , and T 5 . The flywheel diodes D 11 , D 12 , D 21 , D 22 , D 31 , and D32 are respectively linked in an inverse parallel connection with complex semiconductor devices SW 11 , SW 12 , SW 21 , SW 22 , SW 31 , and SW 32 ; moreover, the snubber circuits are also respectively linked in an inverse parallel connection with the complex semiconductor devices SW 11 , SW 12 , SW 21 , SW 22 , SW 31 , and SW 32 , thereby configuring as a whole a motor driving inverter system. Using the complex semiconductor devices SW 11 , SW 12 , SW 21 , SW 22 , SW 31 , and SW 32 of the present invention in the motor driving inverter system, each of the devices SW 11 , SW 12 , SW 21 , SW 22 , SW 31 , and SW 32 can be easily turned on and off by applying and removing a potential to the insulated gate electrode (G) thereof. This unnecessitates such operations of the known device of this kind as an operation in a GTO thyristor to flow and to draw a large amount of current into and from the gate electrode. This leads to an aspect of the present invention that the gate circuit can be remarkably simplified. In addition, since each of the devices SW 11 , SW 12 , SW 21 , SW 22 , SW 31 , and SW 32 uses the saturation characteristic of the MISFET integrated therein, there can be developed a current limiting action even in the thyristor operation. Consequently, a large current can be controlled at a high speed by a low on-state voltage without destroying the complex semiconductor devices. In consequence, as compared with the case where a known device of this kind, for example, a GTO thyristor is utilized in the motor driving inverter system, the inverter system above can be implemented as a small-sized and lightweight apparatus with a decreased loss, a low noise, and the like thanks to easy achievement of a high-frequency operation and easy control thereof. Moreover, also as compared with a case using, for example, the IGBT, there can be implemented a large-capacity and a low-loss inverter system developing a decreased on-state voltage. As described above, according to the present invention, since the thyristor region is added to the IGBT in the best form, the electrons supplied from the cathode electrode via the MIS channel are sufficiently extended to flow in the thyristor region and hence the on-state voltage can be fully lowered without deteriorating the ignition characteristic. That is, the p-type base layer of the IGBT and the p-type base layer of the thyristor region are disposed to be separated from each other and the n-type emitter layer of the thyristor region is partially brought into contact with the n-type base layer so that the MIS current (electrons) and the thyristor current (electrons) flow only through one (series) MISFET, thereby achieving an easy ignition and attaining a low on-state voltage (a large current). In addition, for the p-type base layer of the IGBT and the p-type base layer of the thyristor region, there are partially disposed separated regions below the gate electrode so that the MIS current (electrons) and the thyristor current (electrons) flow at least partially through the channel resistance of one MISFET, thereby achieving an easy ignition and attaining a low on-state voltage (a large current). Consequently, there is obtained an effect that the semiconductor device is operated with a high breakdown voltage and a large current. The present invention has been described with reference to the particular illustrative embodiments.

Claims: A complex semiconductor device comprising: a semiconductor substrate (1) including a pair of principal surfaces (11, 12), a first semiconductor (13) layer of a first conduction type, a second semiconductor layer (14) of a second conduction type being adjacent to the first principal surface (12) and the first semiconductor layer and having an impurity concentration higher than that of the first semiconductor layer, a third semiconductor layer (15) of the second conduction type extending from a second principal surface (11) into the first semiconductor layer and having an impurity concentration higher than that of the first semiconductor layer, a fourth semiconductor layer (16) of the first conduction type extending from the second principal surface into the third semiconductor layer and having an impurity concentration higher than that of the third semiconductor layer, a fifth semiconductor layer (17) of the first conduction type extending from the second principal surface into the first semiconductor layer, being partially brought into contact with the third semiconductor layer and also with the first semiconductor layer, being apart from the fourth semiconductor layer, and having an impurity concentration higher than that of the third semiconductor layer, and a sixth semiconductor layer (18) of the second conduction type being disposed between the first and fifth semiconductor layers, at least one gap being defined between the sixth and the third semiconductor layers to permit said contact for said first and fifth layers, and having an impurity concentration between those respectively of the first and fifth semiconductor layers; a first main electrode (3) being brought into contact via a low resistance with the second semiconductor layer in the first principal surface of the semiconductor substrate; a second main electrode (2) being brought into contact via a low resistance with the third and fourth semiconductor layers in the second principal surface of the semiconductor substrate; and a control electrode (4) formed via an insulation layer on a surface of the third semiconductor layer exposed between the fourth and fifth semiconductor layers in the second principal surface of the semiconductor substrate. A complex semiconductor device according to claim 1, wherein: the first semiconductor layer includes a first layer portion (131) and a second layer portion (132) having an impurity concentration higher than that of the first layer portion and being adjacent to the second semiconductor layer; and the third semiconductor layer includes a first layer portion (151) being adjacent to the first layer portion of the first semiconductor layer and the fifth semiconductor layer and a second layer portion (152) having an impurity concentration higher than that of the first layer portion (151) and being adjacent thereto at a position apart from the second principal surface being brought into contact with the second main electrode and the control electrode of the fourth semiconductor layer. A power transducer including: a pair of dc terminals (T 1 , T 2 ); ac terminals (T 3 ,T 4 ,T 5 ) disposed as many as there are phases of an ac power; inverter units (SB 11 , SW 11 , D 11 , SB 12 , SW 12 , C 12 ; ....) each connected between the pair of dc terminals and each including two circuits each of which including a switching element (SW 11 - SW 33 ) and a diode (D 11 - D 33 ) of an opposite polarity said circuits being connected in series between the pair of dc terminals, interconnecting points of the circuits being connected to different ac terminals, the units being disposed in parallel, as many as there are phases of the ac power, wherein the switching elements have the structure of a complex semiconductor device according to claim 1 or 2.

Inventors: KOBAYASHI HIDEO, KOBAYASHI, HIDEO
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 1994
Main classification: H01L29
IPC codes: H01L29